made a graph of y axis (density g/ml) and x axis (concentration of salt Nacl mass%) what is the slope of the slope?

2 answers

the slope itself it rate of change of density vs concentration

the slope of the slope is the rate of change of that slope, ie, the acceleration of change. That slope of slopes should be constant, if the temperature is held constant.
double check the units of 1st slope is g/ml / %